1. Field of the Invention
The present invention relates to a frequency-stabilized laser apparatus and a method for stabilizing the frequency of a laser, and more particularly to a frequency-stabilized laser apparatus and a method for stabilizing the frequency of a beam emitted from a semiconductor laser.
2. Description of the Related Art
A semiconductor laser has characteristics such as a small size, low power consumption, low cost due to mass production, high efficiency, a long life span of a million hours or more, a wide oscillation wavelength, a wide gain bandwidth, a high output due to the employment of an array structure, and the intensity and the frequency of a beam which can be directly controlled by an applied current, compared with other lasers. Due to such characteristics, the semiconductor laser is widely used in various application fields including optical communication or a light source of a compact disc player.
Among the various application fields, in order to use the laser as a high-precision light source, the frequency of the laser should be stabilized to a predetermined value. A method for stabilizing the frequency of the laser includes a method using spectral lines of atoms, a method using a Fabry-Perot interferometer, and a method using Zeeman effect. In the method using the spectral lines of the atoms, available spectral lines of the atoms are necessary. In addition, since the frequency of the laser can be stabilized only in a specific wavelength and the laser apparatus is complicated, this method is widely used in laboratories rather than industries. In the method using the Fabry-Perot interferometer, the stability is excellent, but a stabilized region is too narrow. Thus, this method is used as auxiliary means of another stabilizing method. The method using the Zeeman effect is representatively and widely used in a He—Ne laser. However, in this case, since the characteristics of a medium are excessively restricted, it is impossible to apply this method to other lasers excluding the He—Ne laser.